Re: [PATCH v10 02/41] iomap: support REQ_OP_ZONE_APPEND

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Nov 10, 2020 at 08:26:05PM +0900, Naohiro Aota wrote:
> A ZONE_APPEND bio must follow hardware restrictions (e.g. not exceeding
> max_zone_append_sectors) not to be split. bio_iov_iter_get_pages builds
> such restricted bio using __bio_iov_append_get_pages if bio_op(bio) ==
> REQ_OP_ZONE_APPEND.
> 
> To utilize it, we need to set the bio_op before calling
> bio_iov_iter_get_pages(). This commit introduces IOMAP_F_ZONE_APPEND, so
> that iomap user can set the flag to indicate they want REQ_OP_ZONE_APPEND
> and restricted bio.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>

Christoph's answers seem reasonable to me, so

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

Er... do you want me to take this one via the iomap tree?

--D

> ---
>  fs/iomap/direct-io.c  | 41 +++++++++++++++++++++++++++++++++++------
>  include/linux/iomap.h |  1 +
>  2 files changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index c1aafb2ab990..f04572a55a09 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -200,6 +200,34 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
>  	iomap_dio_submit_bio(dio, iomap, bio, pos);
>  }
>  
> +/*
> + * Figure out the bio's operation flags from the dio request, the
> + * mapping, and whether or not we want FUA.  Note that we can end up
> + * clearing the WRITE_FUA flag in the dio request.
> + */
> +static inline unsigned int
> +iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
> +{
> +	unsigned int opflags = REQ_SYNC | REQ_IDLE;
> +
> +	if (!(dio->flags & IOMAP_DIO_WRITE)) {
> +		WARN_ON_ONCE(iomap->flags & IOMAP_F_ZONE_APPEND);
> +		return REQ_OP_READ;
> +	}
> +
> +	if (iomap->flags & IOMAP_F_ZONE_APPEND)
> +		opflags |= REQ_OP_ZONE_APPEND;
> +	else
> +		opflags |= REQ_OP_WRITE;
> +
> +	if (use_fua)
> +		opflags |= REQ_FUA;
> +	else
> +		dio->flags &= ~IOMAP_DIO_WRITE_FUA;
> +
> +	return opflags;
> +}
> +
>  static loff_t
>  iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  		struct iomap_dio *dio, struct iomap *iomap)
> @@ -278,6 +306,13 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  		bio->bi_private = dio;
>  		bio->bi_end_io = iomap_dio_bio_end_io;
>  
> +		/*
> +		 * Set the operation flags early so that bio_iov_iter_get_pages
> +		 * can set up the page vector appropriately for a ZONE_APPEND
> +		 * operation.
> +		 */
> +		bio->bi_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);
> +
>  		ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
>  		if (unlikely(ret)) {
>  			/*
> @@ -292,14 +327,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  
>  		n = bio->bi_iter.bi_size;
>  		if (dio->flags & IOMAP_DIO_WRITE) {
> -			bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
> -			if (use_fua)
> -				bio->bi_opf |= REQ_FUA;
> -			else
> -				dio->flags &= ~IOMAP_DIO_WRITE_FUA;
>  			task_io_account_write(n);
>  		} else {
> -			bio->bi_opf = REQ_OP_READ;
>  			if (dio->flags & IOMAP_DIO_DIRTY)
>  				bio_set_pages_dirty(bio);
>  		}
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 4d1d3c3469e9..1bccd1880d0d 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -54,6 +54,7 @@ struct vm_fault;
>  #define IOMAP_F_SHARED		0x04
>  #define IOMAP_F_MERGED		0x08
>  #define IOMAP_F_BUFFER_HEAD	0x10
> +#define IOMAP_F_ZONE_APPEND	0x20
>  
>  /*
>   * Flags set by the core iomap code during operations:
> -- 
> 2.27.0
>